[Tutor] Shifting arrays as though they are a 'word'

Chip Wachob wachobc at gmail.com
Fri Oct 5 16:17:53 EDT 2018


I was not able to find any answers in the archive on this one.

I'm wondering if this task can be done in a better way than what I've

I have an array of bytes.  Up to 64, which makes for 512 bits.

I am reading these bytes in serially, and once I have a collection of
them, I want to shift them by 'n' bits.  The size of the array and the
number of bits are both variable up to the limit of 64/512.

Now, I've played around with looping through the bytes and taking the
LSByte and shifting it by 'n' bits using >> or << and that works for
the first byte.  But then I need to take the next byte in the sequence
and shift it in the opposite direction by 8-n bits using << or >>
(opposite the LSByte direction), respectively.  Then I OR the two
bytes and save them into the location of the LSByte and then move to
the next byte in the sequence and so on.  While this works most of the
time, I sometimes get strange behavior at the 'fringes' of the bytes.
Sometimes I end up with zero, or the shift seems to 'roll over'.

I'm thinking that maybe there's a way to treat the array / list and
shift allowing the bits to transfer from byte to byte as needed.
Maybe by concatenating the bytes into one huge word and then breaking
it apart again?

I'm thinking that you folks out there know of a built-in function, or,
an easier and more predictable way to accomplish the same.

Thank you,

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